1. Field of the Invention
The present invention relates to a combustion system for burning a hydrocarbon-based fuel while suppressing exhaust of gases believed to cause green-house-effect such as carbon dioxide.
2. Description of the Related Art
Several global environmental issues such as an increase in carbon dioxide concentration in air have recently been discussed. When carbon dioxide in air is increased, warming of the earth's climate is promoted, resulting in increase in desert area or sea level elevation. If no countermeasure is taken very soon, a serious environmental disruption might be caused.
The sources for generating carbon dioxide can be classified into a natural source accompanying animal activities and an artificial source accompanying use of vehicles or boilers. Recent abnormal increase in carbon dioxide concentration is said to be caused mainly by the artificial source, especially use of combustion systems.
However, exhaust of carbon dioxide from combustion systems is inevitable as far as a carbon-containing fuel (hydrocarbon-based fuel) is used. When coal, that contains carbon as its main component, is used as the fuel, exhaust amount of carbon dioxide cannot be reduced.
Exothermic reactions of hydrocarbon based fuels such as petroleum and a natural gas include one caused by oxidation of carbon and the one caused by hydrogen. Hence, if carbon components can be separated from a hydrocarbon-based fuel, generation of carbon dioxide can be prevented, as in a case of a hydrogen fuel.
It is, however, very difficult in terms of technology to separate only carbon components from the hydrocarbon-based fuel. For this reason, studies have been recently eagerly made on a combustion system using a hydrocarbon-based fuel to increase the thermal efficiency, thereby obtaining a necessary carolific value with a minimum fuel consumption. However, e.g., a current home boiler using a hydrocarbon-based fuel already has a high thermal efficiency of 80% or more. Even if a thermal efficiency of more than 90% is realized, it will only decrease the exhaust amount of carbon dioxide by as little as a maximum of 10%. Accordingly, improvement in thermal efficiency of a combustion system can hardly decisively solve the problem of carbon dioxide. Similarly, boilers for industrial use or for power plant that use a hydrocarbon-based fuel already have a thermal efficiency of 90% or more. Therefore, it is difficult to further improve the thermal efficiency.
As described above, with a conventional combustion system that uses a hydrocarbon-based fuel, exhaust of carbon dioxide is inevitable. Even if the thermal efficiency of the system is improved to suppress exhaust of carbon dioxide, it will be expected to suppress exhaust as little as a maximum of 10%. Therefore, the problem of realizing drastic exhaust suppression of carbon dioxide cannot be solved with a conventional system that aims at improvement in thermal efficiency.